"I just got told after Tom [Bergeron] announced it. We aren't allowed to know stuff like that," Ballas told reporters after supermodel Petra Nemcova was sent home Tuesday.

"I can't tell you the song, but it will probably be something slow and romantic," said Ballas, who will be dancing with fellow pro Karina Smirnoff while Toscano sings.

The performance comes on a wave of rumors that the Idol finalist and Dancing pro are dating. The two were most recently spotted together this past Monday, when Toscano attended Ballas's concert at The Mint in Los Angeles.

While Ballas will not be joining her at the mic next week, the performance is still something he says he is "looking forward to."

"Pia ... will be amazing," Ballas said. "She is a ridiculously amazing vocalist."